1. Field
Embodiments relate to a rotational position sensor which detects an angle position of a rotating body, and in particular, relates to a contact-type or non-contact type rotational position sensor which detects a rotational angle of a throttle shaft for an engine mounted on a vehicle and the like, a depression angle of an accelerator pedal which is swung around a predetermined axis, and the like.
2. Description of the Related Art
A rotational position sensor known in the related art includes a housing having a bearing hole in the radial direction and a bearing end face in the thrust direction, a rotor having a shaft portion rotatably inserted to the bearing hole of the housing while being contacted to the bearing end face, a return spring which rotationally urges the rotor toward a predetermined rotational angle position, a substrate which is arranged to be opposed to a disk-shaped collar portion formed outside the shaft portion of the rotor in the radial direction within the housing and at which a fixed terminal for detection is formed, a movable contact point arranged at the collar portion of the rotor so as to be contacted to the fixed terminal of the substrate, an arm arranged at the outside of the housing and coupled with the rotor, and the like. With the rotational position sensor, when the rotor is rotated via the arm, the contact position between the movable contact point arranged at the collar portion of the rotor and the terminal arranged on the substrate is varied. The rotation angle position of the rotor (i.e., the arm) is to be detected by detecting current value and the like which vary corresponding to the variation of the angle position. An example of this conventional rotational position sensor may be found in, for example, Japanese Patent Publication 2001-124508.
Another known rotational position sensor includes a housing having a bearing hole in the radial direction, a shaft having a shaft portion rotatably inserted to the bearing hole of the housing, a ring-shaped movable magnet fixed to a disk-shaped collar portion formed outside the shaft portion of the shaft within the housing in the radial direction, a plurality of magnetic plates fixed to the housing so as to sandwich the movable magnet in the direction of the axis line of the shaft, a Hall element arranged between the magnetic plates, and the like. When the shaft is rotated, the relative angle position among the movable magnet (i.e., the north pole and south pole) of the shaft and the magnetic plates and the Hall element fixed to the housing is varied. The rotational angle position of the shaft is to be detected by detecting variation of magnetic fluxes flowing through the Hall element corresponding to the variation of the angle position. An example of this conventional rotational position sensor may be found in, for example, Japanese Patent Publication 2004-150905.
With the above rotational position sensors, the rotor or the shaft portion of the shaft is rotatably supported by the bearing hole of the housing, and then, the movable contact point and fixed terminal or the movable magnet and Hall element etc. for detection are arranged at the outside of the shaft portion in the radial direction. Accordingly, the rotational center of the rotor or the shaft which is to be inherently located at a predetermined position may be varied due to wearing and the like at the outer circumferential face of the shaft portion or the inner circumferential face of the bearing hole. As a result, there is a fear that the relative positional relation between the movable contact point and the fixed terminal or the relative positional relation between the movable magnet and the Hall element is varied and that the rotational position of the rotor or the shaft cannot be detected with high accuracy.
Further, with the rotational position sensors, the movable contact point and fixed terminal or the movable magnet and Hall element etc. for detection are arranged at the outside of the rotor or the shaft portion of the shaft in the radial direction. Accordingly, there has been a problem that an area around the shaft portion cannot be effectively utilized as the arrangement area of the components, which causes an upsizing of the structure.